▷ Sai: what is it, what is it for and what types are there on the market

If you are reading this, it is because you are probably on your PC, or at least you have one at home, where do you connect the power to your PC? In this article we will talk about the UPS, what it is and what it is for on our computer and we will also see what types there are and features, to know what we are facing in the market.

Index of contents

Without a doubt most of us have electronic equipment in our home, all of them depend on electrical energy to function. The power supplies are the bridge between our house and the PC and it is very important that this energy is constant and stable so as not to damage the fragile internal components. In no case would we want to lose our data or buy new components, and if we raise it to the business world, this thought will be even more important.

This is where UPSs appear, some equipment that has traditionally been present in the business world and servers, but it is increasingly common to see them at home and be able to acquire them at relatively cheap prices to give extra protection to our electronic devices. Let's see what a UPS is.

What is a UPS

The acronym UPS comes from the acronym " Uninterruptible Power Supply ", and it is common to find it also by its initials in English UPS (uninterruptible power supply).

The function of a UPS is to provide power to the devices that are connected to it constantly, even when the power supply is cut, these devices will be able to provide power for a time to give us time to store our data and shutdown the computer correctly. For this, this equipment includes a short-life battery system that is activated when it detects that there is no electrical supply at the main outlet.

But it is not only useful for this, also in a team that ensures that the electricity that reaches our computer does so constantly and without spikes and low intensity, in order to preserve the power supply and other components such as the board base. Because the electricity supply is not always constant and varies a lot in poor installations and high consumption situations, we never notice anything because the power supply itself has a system that absorbs these ups and downs if it is of sufficient quality.

So, the faults from which a UPS protects us can be the following:

• Power surges and drops Power outages Unstable power supply Current signal distortion (50 Hz @ 230 V) Prolonged overvoltages

We must bear in mind that our own house has protection elements such as thermomagnetic switches, which protect against overloads and short circuits, and differential switches, which protect us from shunts. But these provide somewhat more basic protection than a UPS and we are also not sure that they are in good condition if they have been installed for a lot of years.

Types of UPS on the market

Depending on its usefulness and the protection characteristics it provides, we can find various types of UPS on the market. Each model will provide us with certain characteristics and will be use-oriented.

The UPS must also have a conversion system between alternating current and direct current, since the batteries will always be supplied with direct current, and the power supply of our PC will be supplied with alternating current.

UPS offline

Offline UPSs are the simplest model we can find on the market, and they are called that because they do not actively protect the PC from prolonged surges or filter the current signal until they reach our PC. In this case it is a device that only protects us from power cuts, by means of a short battery life, and from voltage peaks and point surges at most.

The construction system is the simplest of all, which is based on a line that will go from the power outlet to the PC directly or almost directly, and a charger for the internal battery. When the main current is cut, an inverter will be in charge of converting the direct current from the batteries into alternating current to supply it to the equipment.

Line interactive UPS

We move on to the second type of UPS, which is undoubtedly the one that we will most commonly find in the market with a good relationship between its cost and the advantages it offers us. With it, in addition to correcting voltage peaks and support when there are power failures, it also protects us from undervoltages or prolonged overvoltages and noise in the electrical signal.

To do this, the equipment has a dynamic transformer that acts as a filter to stabilize the current that passes through the UPS to our PC. In this way the electrical signal is corrected to eliminate those spikes that can do so much damage. Otherwise, the current storage system is the same as in the previous case, with a battery system and an inverter to convert that direct current into alternating current.

UPS online

We go to the last type of UPS, which is the most complete of all and provides greater protection. With them, in addition to the previous actions, it will also protect against alternating wave distortions, frequency variations and microcurrent cuts.

For this, these UPSs use a system that completely converts the input current into a completely new signal. The electricity is first transformed into direct current so that it is stored and passes through the batteries, then it is again transformed into alternating current so that it is supplied to the connected PC. In this way the UPS generates a new signal that is totally independent of the one that has entered.

These equipments are used for critical processes such as server cabinets and equipments that need maximum stability and 24/7 operation.

What characteristics should we know to compare a UPS?

The power will be the most important measure to buy a UPS, since it is the one that will determine the amount of energy that will be supplied to our computer, and in no case would we want to fall short, right?

The power in a UPS can be measured in Volt amperes (VA) for being an equipment that works with alternating current and has inductive elements that generate reactive energy, or directly in Watts (W). Let's see a little explanation to understand what VAs are and what differentiates them from Ws.

VA, VAR and W

In this sense, we should know what is the active, reactive, apparent energy and the power factor.

• Active energy: It is the useful energy that an electrical device consumes, we know it well, because it is the one that is measured in watts per hour (Wh) and in terms of power it is measured in Watts (W). An incandescent light bulb for example only consumes active power and its measurement will come in W, just as all electrical devices consume active power and that is why we always see "W" in its technical data sheet. Reactive energy: This energy is generated in certain electrical devices where the use of coils (inductors) to transform the current, generate electromagnetic fields. Motors and transformers, for example, generate reactive energy, and capacitors consume reactive energy. This is measured in reactive volt-amperes per hour (VARh) and its power in reactive volt-amperes (VAR), and it is the energy that we are not interested in having in any case. Apparent energy: it is the sum of the two previous ones, and it is measured in Volt amperes per hour (VAh) and the power in Volt amperes (VA), which is the measure that we could find in an electrical section such as a UPS. Power factor: It is the number that indicates the percentage of active and reactive energy that an apparatus can supply or consume, it is represented as the cosine of φ or cos (φ). The closer to 1 the cos (φ) of an appliance, the less power it will waste. According to ITC-BT-44 of the Low Voltage Electrotechnical Regulation, an electric house must have a cos (φ) of 0.9 or greater to this, otherwise on the invoice there will be surcharges that are not relevant.

Well, in the case of the UPS there are always two values ​​to consider, the W and the VA, and we must know how to calculate the W through their VA to ensure that this equipment has sufficient active power to power our PC.

Calculate power factor

The three measures of power mentioned can be mathematically distributed using a right triangle, this is due to the sinusoidal character of the alternating current. Due to the reactive power, the voltage can advance or lag behind the intensity, so it is all a matter of angles and therefore, these calculations are based on the Pythagorean theorem.

In the previous image we see where the different powers would be placed. Let's imagine that we have a 1200VA and 720W UPS, so the cos (φ) will be, according to Pythagoras:

Cos (φ) = 720/1200 = 0.6

It is not a bad measure, since the upper-mid-range UPSs usually have a power factor between 0.6 and 0.7. Nor should we worry that a UPS has a cos (φ) that does not comply with the REBT of 0.9, this energy will be compensated by other electrical sections and by the favorable capacitors of the UPS. In large companies where the cos (φ) does not comply, capacitor banks are installed.

If for example they gave us the cos (φ) and the reactive power, we would calculate the active power of the UPS as follows:

Active Power = Cos (φ) x 1200 = 0.6 x 1200 = 720 W

We are not going to extend here in circuit theory either because it is not the objective. So, in summary, we must look at these VA, and power factor, or where appropriate, at the output watts of the equipment, and that is equal to or greater than the consumption of the device or devices that we are going to connect to it.

Number of UPS outputs

Another element that we need to know is the number of outputs that our UPS will have. Of course, it will depend on the amount of equipment that we want to connect to it, and the power of each of them. We must also bear in mind that not all UPSs have battery power at all outputs.

In this regard, it will be interesting to see if the UPS has other types of connectors, for example, USB ports for charging mobile phones or USB Type-C for compatible notebooks. Some also have LCD screens to monitor the state of charge of the batteries and other parameters such as consumption.

Battery life for autonomous power

Another essential parameter will be the amount of time that the UPS batteries can supply power. The longer they last, the higher the cost, as is normal.

In addition, we must look at what power these batteries can supply and for how long, so we can more or less know how long we can work without a general power supply.

Conclusion about UPS

UPSs are increasingly used by users of home equipment, especially if we work at home, if our equipment is especially expensive or simply if we know that the electricity supply we have is quite poor. At any given time a UPS can literally save our computer and save us a lot of money.

They started being used by computer companies and professionals, but the decrease in prices, the reduction in space and the increase in benefits, make it one more peripheral to consider when purchasing our equipment. Do you use a UPS, or have you seen one?

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If you have any questions or want to tell us about any curiosity about UPS, write us in the comment box.